1. Technical Field of the Invention
The present invention relates in general to telecommunications networks, and in particular, to managing signaling within telecommunications networks.
2. Description of Related Art
Signaling System no. 7 (SS7) is a signaling network separate from the voice network that is responsible for transmitting control or signaling messages pertaining to either circuit-related information (e.g., call setup, routing, teardown, etc.) or non-circuit related information (e.g., database query, network management, etc.) between signaling points. Examples of signaling points within the SS7 network include Service Switching Points (SSPs), Signal Transfer Points (STPs) and Service Control Points (SCPs).
SSP's are associated with the telephone switches that originate, terminate and/or route calls within a telephone voice network. For example, an SSP can be a combination of a voice switch and an SS7 switch or an adjunct computer connected to the voice switch. The SSP converts signaling from the voice switch into SS7 signaling messages, which can then be sent to other SSP's through the SS7 network. All SS7 messages travel between SSP's through an STP. The STP serves as the router in the SS7 network. The SCP serves as an interface to various databases that store information pertaining to call services, subscribers and networks. For example, such information can include subscriber services, call routing, calling cards, fraud protection and other relevant information.
All SS7 signaling points are interconnected via bidirectional signaling data links. Typically, there are multiple links, collectively referred to as a linkset, between two adjacent signaling points. In order to maintain a high level of reliability, links must remain available for SS7 traffic at all times, with minimal downtime. When a link fails, the other links within its linkset must accept the traffic from the failed link. However, if a link begins to go in and out of service (a condition called a “bouncing link” or “fluctuating link”), this may trigger successive waves of network management messages. The congestion caused by these messages may then result in waves of Integrated Service Digital Network (ISDN) User Part (ISUP) messages resulting from the initial outage.
To minimize the impact to the signaling network caused by a fluctuating signaling link, the SS7 protocol includes procedures for reducing the frequency of fluctuating signaling links. For example, when a link fails, the link is taken out-of-service and enters an alignment phase during which time the link is resynchronized on both ends of the link. After a link has successfully passed the alignment phase, the link is returned to an in-service state, where messages are transmitted and normal processing is allowed. In addition, the link is placed into a probationary period, which lasts the duration of an extended probation timer. If the link fails during the probationary period, the link is again taken out-of-service and all attempts to place the link into alignment are ignored until a suspension timer expires. The suspension timer is used to prevent links from rapidly fluctuating between in-service and out-of-service states.
However, the current protocol is deficient in that a link can continually fail the extended probation timer, and thus continue to cause significant network impact. In order to effectively resolve a bouncing link problem, a network management user must detect the problem by observation of system reports, and then take manual action to remove the offending link from service. Therefore, what is needed is a method for automatically detecting when a signaling link is repeatedly fluctuating in and out of service.